Derivative Financial Instruments Notional Amounts and Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative asset, fair value	$ 375,909	$ 144,371
Derivative liability, gross liability	(183,249)	(76,067)
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Derivative asset, notional amount	446,268	132,260
Derivative liability, notional amount	4,611	9,783
Derivative asset, fair value	11,994	1,123
Derivative liability, gross liability	(61)	(53)
Forward Commitments [Member]
Derivative [Line Items]
Derivative asset, notional amount	0	75,000
Derivative liability, notional amount	414,110	180,000
Derivative asset, fair value	0	63
Derivative liability, gross liability	(1,644)	(371)
Interest Rate Swap with Customer [Member]
Derivative [Line Items]
Derivative asset, notional amount	3,777,684	2,903,489
Derivative liability, notional amount	12,288	376,705
Derivative asset, fair value	375,567	143,484
Derivative liability, gross liability	(2)	(695)
Interest Rate Swap With Counterparty [Member]
Derivative [Line Items]
Derivative asset, notional amount	12,288	376,705
Derivative liability, notional amount	3,777,684	2,903,489
Derivative asset, fair value	2	695
Derivative liability, gross liability	(183,225)	(75,327)
Foreign Exchange Contracts With Customer [Member]
Derivative [Line Items]
Derivative asset, notional amount	2,947	3,373
Derivative liability, notional amount	5,885	7,283
Derivative asset, fair value	32	38
Derivative liability, gross liability	(280)	(154)
Foreign Exchange Contracts With Correspondent Banks [Member]
Derivative [Line Items]
Derivative asset, notional amount	7,325	9,028
Derivative liability, notional amount	2,653	4,976
Derivative asset, fair value	340	192
Derivative liability, gross liability	$ (19)	$ (45)